The invention relates to microscopic examination of an object using a combination of optical microscopy and particle beam microscopy.
For biological and material-science samples in particular, an examination using both optical microscopy, e.g. light microscopy, and particle beam microscopy, e.g. electron microscopy, is often desirable. In the state of the art complex microscopes which can carry out both microscopy methods are used for this. One such microscope is known for example from EP 0849765 A2 or U.S. Pat. No. 6,683,316 B2. Such combination microscopes are complex in particular because the whole of the optical microscope has to be integrated into the vacuum chamber which is required for the particle beam microscopy, and a sample table which moves the sample between both microscopes under a vacuum has to be provided. This results in a relatively large vacuum volume and in addition significant outlay when manufacturing the optical microscope, which then has to be suitable for use under a vacuum. A further disadvantage is that optical imaging with immersion cannot be carried out under a vacuum. If the object is not arranged under a vacuum during the particle beam microscopy, as e.g. in the combination microscope according to US 20080308731 A1, the imaging quality suffers, as the electrons are scattered on a membrane as well as in air.
An alternative to the use of such combination microscopes is the sequential use of single devices. Various designs of holder are used for this in the state of the art. For optical microscopy, glass slides measuring a few centimetres, with cover glasses placed over the sample are customarily used. In electron microscopy, grids a few millimetres in size, or metal sample plates are customary. In order to pass an object to be microexamined, for example a biological sample, from optical microscopy to particle beam microscopy, the sample has to be transferred from one holding system to the other. This involves some disadvantages. Firstly the transfer is time-consuming and carries the risk of damaging or destroying the sample. Secondly providing a location reference in both microscopy methods is difficult, as the position of an area examined e.g. with optical microscopy first has to be found again for particle beam microscopy. Nor does the use of markers in the object or on the biological sample provide further help here, as the structure of the sample changes as a rule during the transfer, e.g. as a result of distortion. A time-consuming and laborious recovery of the object position already microexamined with the other method is thus unavoidable.